Encoding highly compressible NTSC at 800x___

[bjfacca]

Is is ok to set the resolution up to 800x___ when encoding movies with very high compressibility?
I was thinking that maybe setting the resolution to a bigger value than the original 720x480 could decrease quality because it would have to resize up so maybe it would be better to encode at original res and. What you think?
I used to encode all my movies at 640x___, that was stupid but the good thing about it is that when I was going to watch any of my encodes I set the resolution to 640x480 so the movie doesn't get resized during playback at all, and from what i've noticed that improves quality a lot.

Bruno

[dragoman]

Hi,

You are correct in assuming that if you raise the resolution to higher than the original it will look bad. A good rule of thumb is that the less you resize the better, but always resize down or not at all.

If you don't care about file size and you want to encode at the best resolution possible, go ahead and encode at the original resolution. Just be prepared to jack up the bitrate in order to get a decent encode at that resolution.

dragoman

[Acaila]

I disagree with Dragoman. If you've got enough bitrate to justify upsizing, then by all means do it. When you downsize you also lose quality.
By resizing to correct aspect ratio at full resolution you'll lose vertical information, so by upsizing the horizontal res, you can maintain the full vertical resolution and thus get a better picture. Bicubic can handle this perfectly, IF you have enough bits available to make it look good.

[Swede]

by upsizing the horizontal res, you can maintain the full vertical resolution and thus get a better picture. Very interesting!.. I've never thought about this (which shows me that no matter how many .avi's you've done you're still a newbie :)) But, even though you get all the vertical bits, you'll introduce a horizontal error... So, in theory, you should be somewhere in between? Maybe some of the guru's has anything to say.. (No offense Acaila! I have the utmost respect for your postings.)

[Acaila]

But, even though you get all the vertical bits, you'll introduce a horizontal error...
Either you downsize and introduce both horizontal and vertical errors OR you upsize and get only horizontal errors.
But either way you'll introduce errors during playback when your player upsizes again for fullscreen playback.

[Swede]

Sorry, should've been more clear.Either you downsize and introduce both horizontal and vertical errors OR you upsize and get only horizontal errors. What I was trying to say was that: In theory, which is better: *Introducing* bits in one direction OR *reducing* bits in another. That is, if I don't downsize in *both* directions, just one, OR upsize in one direction *not* the other.
I do realize that I'll propably won't be able to note the difference more than other quirks (macroblock and so on) it's just that I always thought that it's more of a problem to enlarge a picture than to reduce..?..
But then I'm not a image-coder. ;)

[dragoman]

Hi,

I was just relating my personal experiences....I also once thought that the higher the resolution, the better. But I found that consistantly when I went over the base resolution of the DVD (720x480) it would introduce artifacts and look bad.

I did some searching and found that by introducing pixels, in effect creating them, encoding took far longer and looked worse than if you resize downward. When you resize downward you are taking pixels out, which is far easier for the codec to compensate for, IMHO, and my encoding results support this.

dragoman